diff options
| -rw-r--r-- | src/compiler/nir/nir_opt_if.c | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/src/compiler/nir/nir_opt_if.c b/src/compiler/nir/nir_opt_if.c index 4d3183ed151..af63b90f249 100644 --- a/src/compiler/nir/nir_opt_if.c +++ b/src/compiler/nir/nir_opt_if.c @@ -1326,6 +1326,65 @@ opt_if_merge(nir_if *nif) return progress; } +/* Perform optimisations based on the values we can derive from the evaluation + * of if-statement conditions. + */ +static bool +opt_for_known_values(nir_builder *b, nir_if *nif) +{ + bool progress = false; + + assert(nif->condition.is_ssa); + nir_ssa_def *if_cond = nif->condition.ssa; + + if (if_cond->parent_instr->type != nir_instr_type_alu) + return false; + + nir_alu_instr *alu = nir_instr_as_alu(if_cond->parent_instr); + switch (alu->op) { + case nir_op_feq: + case nir_op_ieq: { + nir_load_const_instr *load_const = NULL; + nir_ssa_def *unknown_val = NULL; + + nir_ssa_def *src0 = alu->src[0].src.ssa; + nir_ssa_def *src1 = alu->src[1].src.ssa; + if (src0->parent_instr->type == nir_instr_type_load_const) { + load_const = nir_instr_as_load_const(src0->parent_instr); + unknown_val = src1; + } else if (src1->parent_instr->type == nir_instr_type_load_const) { + load_const = nir_instr_as_load_const(src1->parent_instr); + unknown_val = src0; + } + + if (!load_const) + return false; + + /* TODO: remove this and support swizzles? */ + if (unknown_val->num_components != 1) + return false; + + /* Replace unknown ssa uses with the known constant */ + nir_foreach_use_safe(use_src, unknown_val) { + nir_cursor cursor = nir_before_src(use_src, false); + nir_block *use_block = nir_cursor_current_block(cursor); + if (nir_block_dominates(nir_if_first_then_block(nif), use_block)) { + nir_instr_rewrite_src(use_src->parent_instr, use_src, + nir_src_for_ssa(&load_const->def)); + progress = true; + } + } + + break; + } + + default: + return false; + } + + return progress; +} + static bool opt_if_cf_list(nir_builder *b, struct exec_list *cf_list) { @@ -1380,6 +1439,7 @@ opt_if_safe_cf_list(nir_builder *b, struct exec_list *cf_list) progress |= opt_if_safe_cf_list(b, &nif->then_list); progress |= opt_if_safe_cf_list(b, &nif->else_list); progress |= opt_if_evaluate_condition_use(b, nif); + progress |= opt_for_known_values(b, nif); break; } |